# File regex1.pl
# Regular expressions(regex). String =~ /Pattern/  same as String =~ m/Pattern/
# Match (m) the String with Pattern
# Last succesful match. System variables take values:
# 	$` =  first part  $& = fit    $' = last part    
#   position where match is found = length($`) -how many chars are before gives position
#	Sequence=  Too many spaces   Pattern=^s before=  fit=     after= Too many spaces
#	Sequence=  Too many spaces   Pattern=^s* before=  fit=      after=Too many spaces position=0
#	Sequence=  Too many spaces  Pattern=[a-z] before=    fit=T  after=oo many spaces  position=2
#	Sequence=  Too many spaces  Pattern=oo before=  T  fit=oo  after= many spaces position=3
#	Sequence=  Too many spaces  Pattern=[m|n] before=  Too   fit=m  after=any spaces position=6
#	Sequence=  Too many spaces  Pattern=s.*s before=  Too many   fit=spaces  after= position=11
$seq = '  Too many spaces';  #there are 2 spaces before Too
# Begins with 1 space
$seq =~ m/^\s/;
print "\nSequence=$seq   Pattern=^\s before=$`  fit=$&    after=$' " ;
# Begins with any number of spaces
$seq =~ m/^\s*/;
print "\nSequence=$seq   Pattern=^\s* before=$`  fit=$&    after=$' position=", length($`);  
# Match first letter [a-z] lower case but oignore case (i)
$seq =~ m/[a-z]/i;
print "\nSequence=$seq  Pattern=[a-z] before=$`  fit=$&  after=$' position=", length($`);
# find first oo ignore case
$seq =~ m/oo/i;
print "\nSequence=$seq  Pattern=oo before=$`  fit=$&  after=$' position=", length($`);
# look for first m OR n
$seq =~ m/[m|n]/;
print "\nSequence=$seq  Pattern=[m|n] before=$`  fit=$&  after=$' position=", length($`);
# look for a word that starts with s and ends with s. Any number of chars is .*
$seq =~ m/s.*s/;
print "\nSequence=$seq  Pattern=s.*s before=$`  fit=$&  after=$' position=", length($`);