#!/usr/bin/perl

use strict;
use warnings;

use Regexp::Common;

while (<DATA>) {
    s|($RE{num}{decimal})%|$1 * 0.01|eg;
    print;
}

__DATA__
ENSP00000233379 1058 30 1206 1298 96.1% 13 + 96524483 96533474 8992
ENSP00000233379 1058 30 1206 1298 96% 13 + 96524483 96533474 8992

##</code><code>##

    s|\b($RE{num}{decimal})%|$1 * 0.01|eg;

##</code><code>##

    if (/%/) {
       print STDERR "Input has been corrupted!";
       # die ?
    }