#!perl
$_='x_$foo';
$pat = "foo";
print "Line == <<$_>>\n";
if(/x_.$pat/) {
    print "found x-pat\n";
} 
if(/x_\$$pat/) {
    print "found x-slash-dollar-pat\n";
} 
if(/x_\\$$pat/) {
    print "found x-twoslash-dollar-pat\n";
} 
if(/x_\\\$$pat/) {
    print "found x-threeslash-dollar-pat\n";
} 
if(/x_[\$]$pat/) {
    print "found x-brace-dollar-pat\n";
}