Another solution involves a negative lookahead assertion (see perlre): 

if ( /^if(?!f)/ ) {
  # begins with if (but not with iff)
}
else {
  # anything else
}

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The (?!f) part imposes a zero-width condition on the match: it must not be followed by the character 'f'. The difference between this solution and /^if[^f]/ is that the latter regex fails on the string 'if'. In other words, with the negative lookahead, the match has length 2, whereas with a (negative) character class the match has length 3.

the lowliest monk

In reply to Re: regex problem by tlm
in thread regex problem by mosh

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