use strict;
my $str = '
1 Agra Achhnera NIL
2 Agra Agra NIL
3 Agra Fatehabad NIL
4 Agra Fatehpur Sikri NIL
5 Agra Jagner NIL
6 Agra Jarar NIL
7 Agra Khairagarh NIL
8 Agra Shamshabad NIL
9 Aligarh Atrauli NIL
10 Aligarh Chharra NIL
11 Aligarh Aligarh 1300.00
12 Aligarh Khair 1300.00
13 Allahabad Allahabad NIL';
my $regex = qr/([a-zA-Z]+)\s([a-zA-Z]+)/p;
my $subst = '\\1\\2';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html