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Hi, new questions go in Seekers Of Perl Wisdom because

Roy Johnson, whom you asked a question, hasn't been here in 6 weeks.

You used code tags and put your code in between, that is awesome :)

Welcome, see How do I post a question effectively?, Where should I post X?

The regex which is not working for you, contains A zero-width negative look-ahead assertion, and like perlre#(?!pattern) says

A zero-width negative look-ahead assertion. For example /foo(?!bar)/ matches any occurrence of "foo" that isn't followed by "bar". Note however that look-ahead and look-behind are NOT the same thing. You cannot use this for look-behind.

If you are looking for a "bar" that isn't preceded by a "foo", /(?!foo)bar/ will not do what you want. That's because the (?!foo) is just saying that the next thing cannot be "foo"--and it's not, it's a "bar", so "foobar" will match. Use look-behind instead (see below).

So, use a look-behind

But, that probably won't work either, because you can't have variable length length lookbehind , so you need to use a fixed width lookbehind.

#!/usr/bin/perl -- use strict; use warnings; use Test::More qw' no_plan '; Main(@ARGV); exit(0); sub Main { my @yesWant = ( 'equity, private equity', 'equity', 'private equity,equity', 'private equity, equity', 'equity,private equity', ); my @notWant = ( 'private equity', 'private equity', 'mutual funds', 'cds', ); for my $not ( @notWant ){ ok( (not TestEquity($not)), "not '$not'" ); } for my $yes ( @yesWant ){ ok( TestEquity($yes), "yes '$yes'" ); } } sub TestEquity { return 1 if $_[0] =~ m/(?<!private\s)equity/; return 0; } __END__ $ prove -v pm911357.lookbehind.pl pm911357.lookbehind.pl .. ok 1 - not 'private equity' ok 2 - not 'private equity' ok 3 - not 'mutual funds' ok 4 - not 'cds' ok 5 - yes 'equity, private equity' ok 6 - yes 'equity' ok 7 - yes 'private equity,equity' ok 8 - yes 'private equity, equity' ok 9 - yes 'equity,private equity' 1..9 ok All tests successful. Files=1, Tests=9, 0 wallclock secs ( 0.06 usr + 0.01 sys = 0.08 CPU +) Result: PASS

If fixed width lookbehind doesn't work for you, simply do TWO tests


In reply to Re^2: Using Look-ahead and Look-behind by Anonymous Monk
in thread Using Look-ahead and Look-behind by Roy Johnson

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