use Bufferlass;
...
my $bufferlass = Bufferlass->new();
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Your module/package is named Bufferlass::Bufferlass, and its relative file path is Bufferlass/Bufferlass.pm. Therefore you want:

use Bufferlass::Bufferlass;
...
my $bufferlass = Bufferlass::Bufferlass->new();
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Or maybe you want to rename your package to just 'Bufferlass', and put the pm file in the directory above where it currently is. Look at where some of the standard modules are relative to @INC, and what their package names are (e.g. Env, File::Copy).