The public-facing docs for this are in $^H; take careful note of the warning in the first paragraph.

The names and meanings of the values are available internally from grep 'define \+HINT' perl.h, starting around line 5939 at the time of writing. However you will normally see the values described there only during compilation time, since that is when they're supposed to take effect. Thus:

% perl -we 'use strict; BEGIN { printf "%#x\n", $^H }'
0x7e2
%
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.. i.e. strict is enabled (STRICT_VARS, STRICT_SUBS, STRICT_REFS), it was enabled by an explicit use strict (EXPLICIT_STRICT_VARS etc), and I'm guessing BLOCK_SCOPE just means we're in a block (the BEGIN block).