It was fun and informative reading your detailed reply roboticus :) It was clever to use $equal as a yes/no flag. I had solved the program like this, yesterday night(I'm entering different no.s and thinking ways where the program breaks)But now I consider your example superior. Anyway look at this:

#!/usr/bin/perl
use warnings;
print "Enter a number\n";
chomp( $a = <stdin> );
print "Enter second number\n";
chomp( $b = <stdin> );
print "Enter third number\n";
chomp( $c = <stdin> );

$big   = 0;
$equal = 0;

if ( $a == $b ) {
    $big   = $a;
    $equal = $a;
}
elsif ( $a > $b ) {
    $big = $a;
}
else {
    $big = $b;
}
if ( $equal == $c ) {
    print "All numbers are same";
}
elsif ( $big < $c ) {
    $big = $c;
    print "The biggest number is $big \n";
}
else {
    print "The biggest number is $big \n";
}
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Having done so, it's easier to see at least one of the errors: In your reporting section, one of your if branches doesn't print anything, so if you entered 1, 2, 3 as your numbers, then $big would be less than $c, and nothing would be printed:

I completely agree. I would've spotted that error if i had formatted well. A big thank you to PerlMonk for correcting my errors patiently. :)