#!/usr/bin/perl -w -l --  
@ARGV = qw[ foo bar baz ];
use threads;
$|=1;
sub f :locked {
    my $tid = threads->self()->tid();
    print "A}$tid}$_[0]";
    select undef, undef, undef, rand(2);
    print "B}$tid}$_[0]";
}
threads->create(\&f, $_) for @ARGV;
$_->join() for threads->list() 
__END__

A}1}foo
A}2}bar
A}3}baz
B}3}baz
B}2}bar
B}1}foo


#!/usr/bin/perl -w -l --  
@ARGV = qw[ foo bar baz ];
use threads;
$|=1;
sub f :locked {
    my $tid = threads->self()->tid();
    print "A}$tid}$_[0]";
    select undef, undef, undef, rand(2);
    print "B}$tid}$_[0]";
}
threads->create(\&f, $_) for @ARGV;
$_->join() for threads->list() 
__END__

A}1}foo
A}2}bar
A}3}baz
B}1}foo
B}2}bar
B}3}baz