use strict;
use warnings;

my $string = "ASBSDEC 34 GADVVEEVEETTE 56 IOEOREAK GKJEOG EFEAF 1090 DAFFEE 376";

my $max;  # This is undefined until set
while ($string =~ /(\d+)/g) {
    if (!defined($max) or $max < $1) {
        $max = $1;
    }
}

print "Max value is $max\n";