Just check the variable for data. 
#!/usr/bin/perl
use CGI qw/:standard/;
print header;

$form_field = param("form_field"); # get the value from form
if ($form_field eq ""){            # if value is nothing
&print_error;                      # run subroutine
}else{                             # else
print "$form_field\n";             # do your stuff
}

sub print_error{                   # Error subroutine
print "there was an error\n";
}

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In reply to Re: Empty form fields error message by nlafferty
in thread Empty form fields error message by n4mation

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