Surely trying to match \s* is futile in a negative-lookup? Because \s* can match nothing it will always succeed, thereby never matching?? I tried using \s+.

The following code:

#!/usr/bin/perl -w
use strict;

my @strings = ( "Foo::Bar()",
                "Foo::Bar ()",
                "Foo::Bar   ()",
                "  Foo::Bar()",
                "  Foo::Bar  ()"
                );

my %test = ( 1 => qr/Foo::Bar(?!\s*\()/,
             2 => qr/Foo::Bar(?!\s+\()/
             );

[download]

foreach my $teststring ( @strings )
{
    print( "---$teststring---\n" );
    foreach my $testnum ( sort { $a <=> $b } keys %test )
    {
        if ( $teststring =~ m/$test{$testnum}/ )
        {
            print( "test $testnum matches\n" );
        }
        else
        {
            print( "test $testnum does not match\n" );
        }
    }
}

[download]
produces the following output
---Foo::Bar()---
test 1 does not match
test 2 matches
---Foo::Bar ()---
test 1 does not match
test 2 does not match
---Foo::Bar   ()---
test 1 does not match
test 2 does not match
---  Foo::Bar()---
test 1 does not match
test 2 matches
---  Foo::Bar  ()---
test 1 does not match
test 2 does not match

[download]

In reply to Re: Negative Lookahead Assertion Problem by monarch
in thread Negative Lookahead Assertion Problem by Limbic~Region

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