my $string = "abcdefDaveghijkl";
if ( $string =~ /Dave/ ) {
    print "I found Dave.\n";
}

##</code><code>##

my $string = "1.23.45";
print "Found a number.\n" if /\d+/;

##</code><code>##

my $string = "1.234.567.txt";
print "Found a good filename.\n" if /\d+\.txt/;

##</code><code>##

my $string = "1.234.567.txt";
print "Match.\n" if /567.txt/;

##</code><code>##

/^\d+\.txt/

##</code><code>##

my $testname = "     456.txt";
my $filename;
if ($filename = $testname=~ /^\s*?(\d+\.txt)\s*?$/ ) {
   print "Found a file named $filename.\n";
}