diff --git a/src/tools/check_keywords.pl b/src/tools/check_keywords.pl
index 8d0d962..a5a01d2 100755
--- a/src/tools/check_keywords.pl
+++ b/src/tools/check_keywords.pl
@@ -1,111 +1,109 @@
-#!/usr/bin/perl -w
+#!/usr/bin/perl
 
 use strict;
+use warnings;
+use diagnostics;
+use Carp;
 
 # Check that the keyword lists in gram.y and kwlist.h are sane. Run from
 # the top directory, or pass a path to a top directory as argument.
 #
 # $PostgreSQL$
 
-my $path;
+local $, = ' ';        # set output field separator
+local $\ = "\n";        # set output record separator
 
-if (@ARGV) {
-	$path = $ARGV[0];
-	shift @ARGV;
-} else {
-	$path = "."; 
-}
-
-$[ = 1;			# set array base to 1
-$, = ' ';		# set output field separator
-$\ = "\n";		# set output record separator
+my $path =  $ARGV[0] || '.';
 
-my %keyword_categories;
-$keyword_categories{'unreserved_keyword'} = 'UNRESERVED_KEYWORD';
-$keyword_categories{'col_name_keyword'} = 'COL_NAME_KEYWORD';
-$keyword_categories{'type_func_name_keyword'} = 'TYPE_FUNC_NAME_KEYWORD';
-$keyword_categories{'reserved_keyword'} = 'RESERVED_KEYWORD';
+my %keyword_categories = (
+    unreserved_keyword     => 'UNRESERVED_KEYWORD',
+    col_name_keyword       => 'COL_NAME_KEYWORD',
+    type_func_name_keyword => 'TYPE_FUNC_NAME_KEYWORD',
+    reserved_keyword       => 'RESERVED_KEYWORD',
+);
 
 my $gram_filename = "$path/src/backend/parser/gram.y";
-open(GRAM, $gram_filename) || die("Could not open : $gram_filename");
 
-my ($S, $s, $k, $n, $kcat);
+my ($S, $s, $k, $kcat);
 my $comment;
-my @arr;
 my %keywords;
 
-line: while (<GRAM>) {
-    chomp;	# strip record separator
+open my $gram, '<', $gram_filename or croak "Could not open $gram_filename: $!";
+my @grammar = <$gram>;
+close $gram;
+line: foreach (@grammar) {
+    chomp;    # strip record separator
 
     $S = $_;
     # Make sure any braces are split
-    $s = '{', $S =~ s/$s/ { /g;
-    $s = '}', $S =~ s/$s/ } /g;
+    $s = '{'; $S =~ s/$s/ { /xg;
+    $s = '}'; $S =~ s/$s/ } /xg;
     # Any comments are split
-    $s = '[/][*]', $S =~ s#$s# /* #g;
-    $s = '[*][/]', $S =~ s#$s# */ #g;
+    $s = '[/][*]'; $S =~ s#$s# /* #xg;
+    $s = '[*][/]'; $S =~ s#$s# */ #xg;
 
     if (!($kcat)) {
-	# Is this the beginning of a keyword list?
-	foreach $k (keys %keyword_categories) {
-	    if ($S =~ m/^($k):/) {
-		$kcat = $k;
-		next line;
-	    }
-	}
-	next line;
+    # Is this the beginning of a keyword list?
+    foreach my $k (keys %keyword_categories) {
+        if ($S =~ m/^($k):/x) {
+            $kcat = $k;
+            next line;
+        }
+    }
+    next line;
     }
 
     # Now split the line into individual fields
-    $n = (@arr = split(' ', $S));
+    my @arr = split(' ', $S);
+    
+    my %comment_switch = (
+        '*/' => 0,
+        '/*' => 1,
+    );
 
     # Ok, we're in a keyword list. Go through each field in turn
-    for (my $fieldIndexer = 1; $fieldIndexer <= $n; $fieldIndexer++) {
-	if ($arr[$fieldIndexer] eq '*/' && $comment) {
-	    $comment = 0;
-	    next;
-	}
-	elsif ($comment) {
-	    next;
-	}
-	elsif ($arr[$fieldIndexer] eq '/*') {
-	    # start of a multiline comment
-	    $comment = 1;
-	    next;
-	}
-	elsif ($arr[$fieldIndexer] eq '//') {
-	    next line;
-	}
-
-	if ($arr[$fieldIndexer] eq ';') {
-	    # end of keyword list
-	    $kcat = '';
-	    next;
-	}
-
-	if ($arr[$fieldIndexer] eq '|') {
-	    next;
-	}
-	
-	# Put this keyword into the right list
-	push @{$keywords{$kcat}}, $arr[$fieldIndexer];
+    for (0..$#arr) {
+        if ($arr[$_] eq '//') {
+            next line;
+        }
+
+        if (exists $comment_switch{$arr[$_]}) {
+            $comment = $comment_switch{$arr[$_]};
+            next;
+        }
+
+        if ($comment) {
+            next;
+        }
+
+        if ($arr[$_] eq ';') {
+            # end of keyword list
+            $kcat = '';
+            next;
+        }
+
+        if ($arr[$_] eq '|') {
+            next;
+        }
+
+        # Put this keyword into the right list
+        push @{$keywords{$kcat}}, $arr[$_];
     }
 }
-close GRAM;
 
 # Check that all keywords are in alphabetical order
-my ($prevkword, $kword, $bare_kword);
-foreach $kcat (keys %keyword_categories) {
+my ($prevkword, $bare_kword);
+foreach my $kcat (keys %keyword_categories) {
     $prevkword = '';
 
-    foreach $kword (@{$keywords{$kcat}}) {
-	# Some keyword have a _P suffix. Remove it for the comparison.
-	$bare_kword = $kword;
-	$bare_kword =~ s/_P$//;
-	if ($bare_kword le $prevkword) {
-	    print "'$bare_kword' after '$prevkword' in $kcat list is misplaced";
-	}
-	$prevkword = $bare_kword;
+    foreach my $kword (@{$keywords{$kcat}}) {
+    # Some keyword have a _P suffix. Remove it for the comparison.
+    $bare_kword = $kword;
+    $bare_kword =~ s/_P$//x;
+    if ($bare_kword le $prevkword) {
+        print "'$bare_kword' after '$prevkword' in $kcat list is misplaced";
+    }
+    $prevkword = $bare_kword;
     }
 }
 
@@ -115,7 +113,7 @@ foreach $kcat (keys %keyword_categories) {
 # with a dummy value.
 my %kwhashes;
 while ( my ($kcat, $kcat_id) = each(%keyword_categories) ) {
-    @arr = @{$keywords{$kcat}};
+    my @arr = @{$keywords{$kcat}};
 
     my $hash;
     foreach my $item (@arr) { $hash->{$item} = 1 }
@@ -126,66 +124,69 @@ while ( my ($kcat, $kcat_id) = each(%keyword_categories) ) {
 # Now read in kwlist.h
 
 my $kwlist_filename = "$path/src/include/parser/kwlist.h";
-open(KWLIST, $kwlist_filename) || die("Could not open : $kwlist_filename");
 
 my $prevkwstring = '';
 my $bare_kwname;
 my %kwhash;
-kwlist_line: while (<KWLIST>) {
-    my($line) = $_;
-
-    if ($line =~ /^PG_KEYWORD\(\"(.*)\", (.*), (.*)\)/)
-    {
-	my($kwstring) = $1;
-	my($kwname) = $2;
-	my($kwcat_id) = $3;
-
-	# Check that the list is in alphabetical order
-	if ($kwstring le $prevkwstring) {
-	    print "'$kwstring' after '$prevkwstring' in kwlist.h is misplaced";
-	}
-	$prevkwstring = $kwstring;
-
-	# Check that the keyword string is valid: all lower-case ASCII chars
-	if ($kwstring !~ /^[a-z_]*$/) {
-	    print "'$kwstring' is not a valid keyword string, must be all lower-case ASCII chars";
-	}
-
-	# Check that the keyword name is valid: all upper-case ASCII chars
-	if ($kwname !~ /^[A-Z_]*$/) {
-	    print "'$kwname' is not a valid keyword name, must be all upper-case ASCII chars";
-	}
-
-	# Check that the keyword string matches keyword name
-	$bare_kwname = $kwname;
-	$bare_kwname =~ s/_P$//;
-	if ($bare_kwname ne uc($kwstring)) {
-	    print "keyword name '$kwname' doesn't match keyword string '$kwstring'";
-	}
-
-	# Check that the keyword is present in the grammar
-	%kwhash = %{$kwhashes{$kwcat_id}};
-
-	if (!(%kwhash))	{
-	    #print "Unknown kwcat_id: $kwcat_id";
-	} else {
-	    if (!($kwhash{$kwname})) {
-		print "'$kwname' not present in $kwcat_id section of gram.y";
-	    } else {
-		# Remove it from the hash, so that we can complain at the end
-		# if there's keywords left that were not found in kwlist.h
-		delete $kwhashes{$kwcat_id}->{$kwname};
-	    }
-	}
+
+open my $kwlist, '<', $kwlist_filename or croak "Could not open $kwlist_filename: $!";
+my @kwlist_lines = <$kwlist>;
+close $kwlist;
+kwlist_line: foreach (@kwlist_lines) {
+    my($kwstring, $kwname, $kwcat_id);
+    if (m{^PG_KEYWORD \( \"(.*)\", \s (.*), \s (.*) \) }x) {
+        ($kwstring, $kwname, $kwcat_id) = ($1, $2, $3);
+    }
+    else {
+        next kwlist_line;
+    }
+
+    # Check that the list is in alphabetical order
+    if ($kwstring le $prevkwstring) {
+        print "'$kwstring' after '$prevkwstring' in kwlist.h is misplaced";
+    }
+    $prevkwstring = $kwstring;
+
+    # Check that the keyword string is valid: all lower-case ASCII chars
+    if ($kwstring !~ /^[a-z_]*$/x) {
+        print "'$kwstring' is not a valid keyword string, must be all lower-case ASCII chars";
+    }
+
+    # Check that the keyword name is valid: all upper-case ASCII chars
+    if ($kwname !~ /^[A-Z_]*$/x) {
+        print "'$kwname' is not a valid keyword name, must be all upper-case ASCII chars";
+    }
+
+    # Check that the keyword string matches keyword name
+    $bare_kwname = $kwname;
+    $bare_kwname =~ s/_P$//x;
+    if ($bare_kwname ne uc($kwstring)) {
+        print "keyword name '$kwname' doesn't match keyword string '$kwstring'";
+    }
+
+    # Check that the keyword is present in the grammar
+    %kwhash = %{$kwhashes{$kwcat_id}};
+
+    if (!(%kwhash))    {
+        #print "Unknown kwcat_id: $kwcat_id";
+    }
+    else {
+        if (!($kwhash{$kwname})) {
+            print "'$kwname' not present in $kwcat_id section of gram.y";
+        }
+        else {
+            # Remove it from the hash, so that we can complain at the end
+            # if there's keywords left that were not found in kwlist.h
+            delete $kwhashes{$kwcat_id}->{$kwname};
+        }
     }
 }
-close KWLIST;
 
 # Check that we've paired up all keywords from gram.y with lines in kwlist.h
 while ( my ($kwcat, $kwcat_id) = each(%keyword_categories) ) {
     %kwhash = %{$kwhashes{$kwcat_id}};
 
     for my $kw ( keys %kwhash ) {
-	print "'$kw' found in gram.y $kwcat category, but not in kwlist.h"
+        print "'$kw' found in gram.y $kwcat category, but not in kwlist.h"
     }
 }