my $this = 'hello';
my $thisvar = 'goodbye';

# prints 'hello' of course
print $this;

# single quotes mean no interpolation occurs, prints '$this'
print '$this';

# double quotes invoke interpolation, prints 'hello'
print "$this";

# perl does 'greedy' interpolation (don't know if that's the
# right term) so this prints 'goodbye'
print "$thisvar";

# this makes it explicit that we only want $this, so this
# line prints 'hellovar'
print "${this}var";
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-Mark