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Re: "ee" in Regular Expression: version issue?

by Kenosis (Priest)
on Dec 03, 2012 at 19:52 UTC ( #1006936=note: print w/replies, xml ) Need Help??

in reply to "ee" in Regular Expression: version issue?

Try concatenating the vars for use in the substitution:

use strict; use warnings; my $lhs = '(\d*?)-(.*?)-(.*)'; my $rhs = '$1.$2.$3'; while ( my $var = <DATA> ) { chomp $var; $var =~ s/$lhs/$rhs/ee; print $var, "\n"; } __DATA__ 123-456-789 -456-789 789


123456789 456789 789

From the error message, it appears that the results of the first evaluation is ambiguous to the interpreter when it attempts to evaluate it without the concatenation operator.

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Re^2: "ee" in Regular Expression: version issue?
by kennethk (Abbot) on Dec 03, 2012 at 20:23 UTC

    Or use straight interpolation: my $rhs = '"$1$2$3"';. The key here is that the string literal present after the initial eval (which subs $rhs to its value) is valid Perl code.

    #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

      Yes, excellent. Perhaps the enclosing double-quotes (also) helps to disambiguate the expression. After the first eval, the interpreter sees this:

      $var =~ s/(\d*?)-(.*?)-(.*)/$1$2$3/ee;

      The substituting expression is problematic w/o either being interpolated via "$1$2$3" or concatenated using $1.$2.$3.

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