I still don't understand the steps the interpreter takes when processing an eval

eval with a string argument basically does the same thing as perl when it parses and executes Perl code. The thing that can get confusing is exactly what the contents of that string are. Consider this: when you write $x=3; $y=2; print "$x + $y";, then you know that double quotes interpolate, in this case meaning that the current values of those variables are substituted into the string. What gets passed to the print function is the string "3 + 2". On the other hand, in print '$x + $y';, the single quotes don't interpolate, and the string that gets passed to the function is exactly '$x + $y'. Now substitute eval for print, and I hope it's clear what strings are being passed to the function: In the first case, eval is parsing and executing the Perl code 3 + 2, and in the second case, it's parsing and executing the Perl code $x + $y, with the current values of those variables. Although in this simple example the result may be the same, it can get very tricky very quickly, for example if the code and especially the contents of the variables get more complex, if the string to be evaled gets stored for later execution, and so on.