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Re: Using SprintF in S & R

by herveus (Parson)
on Jul 11, 2017 at 18:06 UTC ( #1194850=note: print w/replies, xml ) Need Help??


in reply to Using SprintF in S & R

Howdy!

The right hand side of s/// does not execute code unless you use the "e" modifier.

So, s/\<time\>(\d+)\<\/time\>/\<time\>sprintf("%06d",$1)\<\/time\>/e is what you want. Note the "e" after the last slash.

Edit to correct placement of "e" modifier. Thanks Laurent. Too many slashes and backslashes!

yours,
Michael

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Re^2: Using SprintF in S & R
by afoken (Canon) on Jul 11, 2017 at 20:37 UTC
    The right hand side of s/// does not execute code unless you use the "e" modifier.

    Would you bet your money on that statement? I would not.

    You are right, s/// usually does not execute code without the /e modifier. But Perl would not be Perl if you could not mess around with that. Note that even if you could mess with perl, you probably should not.

    I'll abuse a trick invented by Andrew Pimlott, that I saw first in the "Perl hardware store" talks (1, 2, 3, 4) by Dominus:

    #!/usr/bin/perl use strict; use warnings; sub TIEHASH { return bless {},$_[0]; } sub FETCH { return $_[1]; } tie my %X,__PACKAGE__; my $foo='look! no eval: 3735928559'; $foo=~s/(\d+)/$X{sprintf '0x%08X',$1}/; print $foo;
    >perl eval.pl look! no eval: 0xDEADBEEF >

    But there is also a way without tie magic. Dereferencing an anonymous array reference:

    #!/usr/bin/perl use strict; use warnings; my $foo='look! no eval: 3735928559'; $foo=~s/(\d+)/${[sprintf '0x%08X',$1]}[0]/; print $foo;
    >perl eval2.pl look! no eval: 0xDEADBEEF >

    Both tricks (ab)use the fact that s/// interpolates the replacement expression, unless you force it not to do so (using ' as the delimiter instead of /).

    Alexander

    --
    Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
Re^2: Using SprintF in S & R
by Laurent_R (Canon) on Jul 11, 2017 at 19:00 UTC
    I guess you mean to have the "e" modifier at the end of the substitution, not after the regex of the statement modifier (the if conditional).

    Besides, I don't think you need to escape the < and > characters.

      Howdy!

      Ack! Thanks for pointing that out. The perils of too much copy and paste.

      yours,
      Michael

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