Useful things you can do with Perl Books on Perl Perl Manuals / Tutorials   1. Execute a system command. The example shown is a DOS command. Change the command when running on a Unix or other operating system. The command executes, and its output is displayed on the screen. # execute a system command. print `dir c:\perl\my_programs\*.pl`; This example captures the return code of the command. You can examine it to see if the command worked. # $x captures return code $x = system('dir c:\perl\my_programs\*.pl');#(example for windows) $x = system('ls ');#(example for unix) print "return code is $x \n"; If you want to capture the output of the command in a file and then possibly read the file in your program, you can use the > operator in the command. The file you specify will be created if it doesn’t exist, and replaced if it does exist. # > places output of command in a file $x = system('dir c:\perl\my_programs\*.pl > c:\perl\my_programs\output.txt'); # display the file $x = system('type c:\perl\my_programs\output.txt');     2. Dropping leading or trailing spaces. #trim leading blanks $text = " My Dog has fleas "; $text =~ s/^\s+//; print "dropped leading blanks: $text\n"; #trim trailing blanks $text = " My Dog has fleas "; $text =~ s/\s+$//; print "dropped trailing blanks: $text xxx \n";   3. Dropping all spaces from a string. # drop all spaces $text = "My Dog has fleas"; $text =~ s/\s+//g;#this worked print "drop all spaces: $text\n"; 4. Replacing a text string by another. # replace text string $text = "My Dog has fleas"; $text =~ s/Dog/cat/; print "replaced string: $text\n";   4. Translating a text string. All occurrences of one character are replaced by another. # translate text string $text = "My Dog has fleas"; $text =~ tr/o/u/; #dog becomes dug print "replaced string: $text\n"; # translate more than one character $text = "My Dog has fleas"; $text =~ tr/oea/uie/; #o becomes u, e -> i, a -> e print "replaced string: $text\n";   5. Splitting up a string at specific column positions. #break at column positions $text = "My Dog has fleas"; $a = substr($text,0,3); $b = substr($text,3,4); $c = substr($text,7,4); $d = substr($text,11,4);#i know it's short by 1 $e = substr($text,21,4);# no such data print "break at column positions \n";print "a $a \n"; print "b $b \n"; print "c $c \n"; print "d $d \n"; print "e $e \n";   6. Splitting a string into words. This will treat leading spaces as a word. You can easily correct that. See the second part of the example. #split into words # this treats leading spaces as a word $text = " My Dog has fleas"; # the + means 1 or more spaces ($a, $b, $c, $d, $e, $f) = split(/ +/,$text); print "splitting at spaces (without dropping leading spaces)\n"; print "a $a \n"; print "b $b \n"; print "c $c \n"; print "d $d \n"; print "e $e \n"; print "f $f \n"; # you may want to drop leading spaces first $text =~ s/^\s+//;#dropping leading spaces ($a, $b, $c, $d, $e, $f) = split(/ +/,$text); print "splitting at spaces (after dropping leading spaces)\n"; print "a $a \n"; print "b $b \n"; print "c $c \n"; print "d $d \n"; print "e $e \n"; print "f $f \n";   7. Concatenating two strings with intervening spaces. #concatenate with spaces $a = "first"; $b = "second"; $v = "$a $b"; print "concatenate with spaces $v \n";   8. Concatenating two strings without intervening spaces. #concatenate without spaces $a = "first"; $b = "second"; $v = $a . $b; print "concatenate without spaces $v \n"; Top of Page