in reply to Matching string containing values between 0 and 100 inclusive

For educational purpose ( see ""(??{ code })" section of perlre). In real code, please use KISS_principle if ($x >= 0 && $x <= 100). 
perl -le '
for $num (qw(-1 0 7 12 88 100 123)) {
   if ($num=~ /^(\d+)(??{$^N >=0 && $^N <= 100 ? "" : "(?!)"})$/) {
       print $1;
   }
}
'

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update: added if clause. update2: added perlre reference.
print+qq(\L@{[ref\&@]}@{['@'x7^'!#2/"!4']});

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Re^2: Matching string containing values between 0 and 100 inclusive
by ikegami (Patriarch) on Mar 17, 2009 at 23:44 UTC

    That compiles a regexp pattern every run. 

    /^(\d+)(??{$^N >=0 && $^N <= 100 ? "" : "(?!)"})$/

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    should be 

    /^(\d+)(?(?{ $^N < 0 || $^N > 100 })(?!))$/

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    And match failures would be cheaper still as 

    /^(\d+)$(?(?{ $^N < 0 || $^N > 100 })(?!))/

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