Uses the value of EXPR as a filename and executes the contents of the file as a Perl script. Its primary use is to include subroutines from a Perl subroutine library. 

    do 'stat.pl';

is just like 


    scalar eval `cat stat.pl`;


##</code><code>##

do ("print");
print $!, "\n" if $!;

##</code><code>##

do print;
print $!, "\n" if $!;

##</code><code>##

$_ = 1;
do print;
print "\n";
print $!, "\n" if $!;

##</code><code>##

$_ = 1;
do (print);
print "\n";
print $!, "\n" if $!;