die "Not supported.\n" if /[^-+0-9x]/;

To avoid  Use of uninitialized value $_ in pattern match (m//) at ... I think this should be
    die "Not supported.\n" if $eq =~ /[^-+0-9x()]/;
or maybe better
    die "Not supported: '$1' \n" if $eq =~ /([^-+0-9x()]+)/;
(both tested).

Give a man a fish:  <%-(-(-(-<

In reply to Re^2: How would you solve a user-inputted simple one-variable Linear Equation by AnomalousMonk
in thread How would you solve a user-inputted simple one-variable Linear Equation by nat47

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