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Re: require different modules per OS?

by gwadej (Chaplain)
on Nov 18, 2009 at 14:57 UTC ( #807927=note: print w/ replies, xml ) Need Help??

in reply to require different modules per OS?

To expand on keszler's comment, use happens at compile time and the if happens at run time.

By moving the use into a string eval, you put off its execution until run time.

G. Wade

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Re^2: require different modules per OS?
by ambrus (Abbot) on Nov 19, 2009 at 20:00 UTC

    I downvoted for the string eval. Don't use string eval unless necessary.

    If you want to do something which is not easy enough to write with the if module, you can still use require in a begin-block:

    BEGIN { if ($^O =~ /win32/) { require Win32::TieRegistry; import Win32 +::TieRegistry Delimiter=>"/", ArrayValues=>0; } }

      I was wondering how eval EXPR compares. We have the following without eval EXPR:

      BEGIN { if ($^O =~ /win32/) { require Win32::TieRegistry; import Win32::TieRegistry Delimiter=>"/", ArrayValues=>0; } }

      The following would be the equivalent using eval EXPR and a minimal expression:

      BEGIN { if ($^O =~ /win32/) { my @import = ( Delimiter=>"/", ArrayValues=>0 ); eval "use Win32::TieRegistry \@import; 1" or die $@; } }

      Or if you extended the expression beyond the necessary:

      BEGIN { if ($^O =~ /win32/) { eval 'use Win32::TieRegistry Delimiter=>"/", ArrayValues=>0; 1 +' or die $@; } }

      So it looks like there's no gain from using eval EXPR.

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