PerlIO::scalar - in-memory IO, scalar IO

A filehandle is opened but the file operations are performed "in-memory" on a scalar variable. All the normal file operations can be performed on the handle. The scalar is considered a stream of bytes. Currently fileno($fh) returns -1. Attempting to open a read-only scalar for writing will fail, and if warnings are enabled, produce a warning.

"PerlIO::scalar" only exists as a stub. One does not need to explicitly "use PerlIO::scalar". perl v5.40.1 2025-07-03 PerlIO::scalar(3perl)

PerlIO::scalar - in-memory IO, scalar IO

my $scalar = ''; ... open my $fh, "<", \$scalar or die; open my $fh, ">", \$scalar or die; open my $fh, ">>", \$scalar or die; or my $scalar = ''; ... open my $fh, "<:scalar", \$scalar or die; open my $fh, ">:scalar", \$scalar or die; open my $fh, ">>:scalar", \$scalar or die;