a generic subroutine which takes a variable name and looks at it's caller's package to see if that variable is defined and if it's defined, returns it's value

Something like this should do (also complies with strictures too).

sub isdef {
  my($var, $pkg) = ( shift, scalar(caller)."::" );

  return unless defined $main::{$pkg};
  return unless defined $main::{$pkg}{$var};
  return unless defined *{ $main::{$pkg}{$var} }{SCALAR};
  return ${ *{ $main::{$pkg}{$var} }{SCALAR} };
}
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Note, this will only work with scalar value types.
HTH

_________
broquaint