#need data2.txt
#23 1
#24523 1
#67 1
#55 1 3

open FILE, "+<", "data2.txt" or die "Cannot open file" ;
my @lines = <FILE>;
foreach (@lines)
{
  #selects '55 1 3'
  if($_ =~ m/ 1 3/)
  {
     print "check characters\n";
     print $_ ;
  }

  #only selects 23 1 and not 24523 1
  if($_ =~ /^23/)
  {
     print "check start of the line and characters\n";
     print $_ ;
  }
}
close FILE;

print "\n\n";
# How to select a word at end of the line
# This will select word 'array' only at the end of string
@myarray = ("How array can be called array" =~ m/([aA-zZ]+$)/g);
print join("::",@myarray);

print "\n\n";
# how to get first whole number
# d matches digit and + after that matches till next char is not number
# $1 is automatically created by PERL
if("2010/04/11" =~ m/(\d+)/)
{
  print "first number ".$1
}

print "\n\n";
# how to get all whole numbers in an array
@myarray = ("2010/04/11" =~ m/(\d+)/g);
print join("::",@myarray);

print "\n\n";
#How to get all whole words in an array
#[aA-zZ] matches alphabet, + after that matches till next char is not alphabet
@myarray = ("How 11 to get 33 words 44 in an array" =~ m/([aA-zZ]+)/g);
print join("::",@myarray);

print "\n\n";
# How to replace a matching string
#s/string to match/string to replace/
my $mystring = "replace me";
$mystring =~ s/replace/replaced/;
print $mystring;

print "\n\n";
# How to replace a matching string - case insensitive
#s/string to match/string to replace/i
my $mystring = "Replace me";
$mystring =~ s/replace/Replaced/i;
print $mystring;

$ perl regularexpression.pl
check start of the line and characters
23 1
check characters
55 1 3


array

first number 2010

2010::04::11

How::to::get::all::whole::words::in::an::array

replaced me

Replaced me

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