Sample output with sleep and yield:
C:\Perl\bin\hw>perl pg5.pl
I like computing! *pause for 1 second*
I'm a perl programmer!
'Thread1' returned Threading in perl is fun!
'Thread2' returned Computing is cool!

C:\Perl\bin\hw>perl pg5.pl
I like computing!
I'm a perl programmer!
'Thread1' returned Threading in perl is fun!
'Thread2' returned Computing is cool!

C:\Perl\bin\hw>perl pg5.pl
I like computing! 
I'm a perl programmer!
'Thread1' returned Threading in perl is fun!
'Thread2' returned Computing is cool!

C:\Perl\bin\hw>