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Re^2: extracting data

by moritz (Cardinal)
on Jun 27, 2012 at 08:25 UTC ( #978582=note: print w/ replies, xml ) Need Help??

in reply to Re: extracting data
in thread extracting data

print "$def\n" if ! $val or $val =~ /^0|1$/;

Note that !$val already covers the case where $val is 0.

Also /^0|1$/ is not what you might think it is. The OR | in regexes has a looser precedence than concatenation, which means the regex is the same as ^0 OR 1$, so it also matches strings like 0foo or bar1.

The correct way to write it is /^(0|1)$/, or if you don't want to create a capture, /^(?:0|1)$/.

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Re^3: extracting data
by kcott (Canon) on Jun 27, 2012 at 09:03 UTC

    ++ Thanks for spotting that. I've updated my node.

    I wasn't aware of the precedence issue: thanks for the good explanation.

    -- Ken

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