You used the syntax of a method call, but the slot filled by the object reference or package name contains an expression that returns a defined value that is neither an object reference nor a package name. Something like this will reproduce the error:

$BADREF = 42;
process $BADREF 1,2,3;
$BADREF->process(1,2,3);

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$ perl -e 'package Foo::Bar; sub Foo {1}; sub Foo::Bar {1}; package main; Foo::Bar->Foo'
Can't call method "Foo" without a package or object reference at -e line 1.

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'Foo::Bar'->Foo