misterperl:

In your original code, you have:

my $x = "016";
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If you leave the quotes out, it would be treated as an octal number. So in the perl source code 016 is an octal number. But when perl converts a string to a number, it doesn't perform any octal, binary or hexadecimal conversions. So this bit of code would treat it as a normal decimal number:

$ perl -e 'my $x="016"+1; print $x,"\n"'
17
$
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When you use eval, you can treat a string as a bit of perl source code, so it will be treated as an octal number:

$ perl -e 'my $x=eval "016"; print $x,"\n"'
14
$
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Update: I should've read the rest of the thread before replying, Anonymonk already said this.

...roboticus

When your only tool is a hammer, all problems look like your thumb.