Given the string input and 'input' and 'tinput' and ' input' and 'input ' and input, I want to produce (through substitutive pattern matching) the following string OUTPUT and 'input' and 'tinput' and ' OUTPUT' and 'OUTPUT ' and OUTPUT (that is, substitute occurences of "input" with "OUTPUT" where "input" is surrounded by word boundaries (\b) except when those word boundaries are both followed by single quotes)

My Perl version (5.004?) doesn't seem to support the negative lookbehind regex extension (?<!PATTERN), but it does support the negative lookahead extension (?!PATTERN) ( my sysadmin is unwilling to upgrade Perl, so I'm stuck with this version).

I've come up with s/\b$input_string\b(?!')/$output_string/g (where $input_string = "input" and $output_string = "OUTPUT"), but that produces OUTPUT and 'input' and 'tinput' and ' input' and 'OUTPUT' and OUTPUT, which is not quite right.

I've tried a bunch of other code as well, none of which works correctly... Anybody have any suggestions?

In reply to complex pattern matching by christopherbarsuk

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