101
1
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then 101 x 1 is 101 which is greater or equal to 100.

You probably wanted to compare just the $num? Also, don't use double quotes around variables, especially when using numeric comparison or operators:

#!/usr/bin/perl
use warnings;
use strict;

print 'Enter a string '; 
my $string = <STDIN>;
print 'Enter value ';
chomp( my $num = <STDIN> );

if ($num >= 100) {
    print "Too big, bye\n";
} else {
    my $result = $string x $num;
    print "The result is:\n$result";
}
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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