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How do I match this without lookbehind?

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Contributed by tedv on Dec 08, 2000 at 05:48 UTC
Q&A  > regular expressions


Description:

Suppose I have a string that matches /^(\~?.)*$/ and I want to split it into each atomic piece that would be matched by (\~?.). How would I code such a regular expression for split? I'd like to use lookbehind, crafting an expression that says, "Split after every non-tilde character", but my O'Reilly Regular Expression book says that perl doesn't support lookbehind. Any suggestions?

-Ted

Answer: How do I match this without lookbehind?
contributed by Adam

my @results = grep {$_} split /([~]*?[^~])/, $input;
Answer: How do I match this without lookbehind?
contributed by chipmunk

When the Regular Expressions book was published, the latest version of Perl was 5.005_03. As of 5.6.0, Perl does support lookbehind.

However, you really don't need lookbehind or split to solve this problem: @matches = $string =~ /~?./g;

Answer: How do I match this without lookbehind?
contributed by runrig

Sometimes split is not the best answer for splitting:

my @results; push @results, $1 while /(~?.)/g;
Answer: How do I match this without lookbehind?
contributed by Shakya

my @results = $string =~ m!([^~]+)!g;
Answer: How do I match this without lookbehind?
contributed by I0

Perl v5.6.0 does suport lookbehind

split /(?<=[^~])/ #or split /(?<!~)/ #or /(~?.)/g

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