my $Bpod = 'B<(.*?)>'; my $B = '<b>';    
                           my $b = '</b>';   
    my $Ipod = 'I<(.*?)>'; my $I = '<i>';    
                           my $i = '</i>';   
    my $Upod = 'U<(.*?)>'; my $U = '<u>';    
                           my $u = '</u>';

    open(DATA, "<file.pod");
    my @file = <DATA>;

    s/$Bpod/$B$1$b/gi for @file;
    s/$Ipod/$I$1$i/gi for @file;
    s/$Upod/$U$1$u/gi for @file;