PEM-encoded private keys are multi-line text blobs that start with the line
-----BEGIN <x> PRIVATE KEY-----
and end with the line
-----END <x> PRIVATE KEY-----
The following variation is also possible:
-----BEGIN PRIVATE KEY-----
[...]
-----END PRIVATE KEY-----
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----