sort { ($a =~ /(\d+)/)[0] <=> ($b =~ /(\d+)/)[0] }
sort { ($a =~ /\d+/g)[0]  <=> ($b =~ /\d+/g)[0]  }
sort { (split /;/, $a)[0] <=> (split /;/, $b)[0] }

##</code><code>##

# ST
my @sorted = map  $_->[1],
             sort { $a->[0] <=> $b->[0] }
             map  [ (split /;/)[0], $_], 
             @lines;

# OM
use Syntax::Construct qw{ // };
my %cache;
my @sorted = sort {
                 $cache{$a} //= (split /;/, $a)[0]
                 <=>
                 $cache{$b} //= (split /;/, $b)[0]
             } @lines;

##</code><code>##

sort { $a <=> $b } @lines