Thanks ... i figured the logic out the first time round except that I could
not see how the for is called before the regexp is done. But I see it now ...
i was going to suggest a solution using map actually like
print "yipe\n" if map {/dd_\w+/} keys %hash;
not sure if this would be better ... try running some benchmark on it ...
On Fri, Aug 24, 2001 at 12:13:34PM -0400, Bob Showalter shaped the electrons to read:
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> > Sent: Friday, August 24, 2001 11:54 AM
> > To: Bob Showalter
> > Cc: '[EMAIL PROTECTED]'
> > Subject: Re: test presence of hash key with regexp?
> >
> >
> > Hmm i dont get how
> > /add_\w+/ and print("Yippie!\n"), last for keys %hash;
> > works ... the regexp will be checking $_ right?
>
> /add_\w+/ and print("Yippie!\n"), last for keys %hash;
> ^^^^^^^^^^^^^^^
> This iterates over
> the keys, setting
> $_ to each key
>
> /add_\w+/ and print("Yippie!\n"), last for keys %hash;
> ^^^^^^^^^
> This checks $_ and
> evaluates to true
> (scalar context)
> if a match found
>
> /add_\w+/ and print("Yippie!\n"), last for keys %hash;
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> If a match is found, this part
> is evaluated. First the print,
> then the last. last just stops
> the for loop. Note use of "and"
> to achieve lower precedence than
> comma operator.
>
> Really, grep() is probably the more straightforward way
> to write this, and is what should probably be used:
>
> print "Yippee!\n" if grep(/add_\w+/, keys %hash);
>
> But grep() builds a list of all matches (unless the Perl
> optimizer can optimize this away), while the other solution
> doesn't.
>
> This might be more efficient still, since the list of keys
> wouldn't need to be created:
>
> /add_\w+/ and print("Yippie!\n"), last while ($_, undef) = each %hash;
>
>
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