Template:P1

The template {{P1}} returns its first parameter.

[edit] Pn

The templates {{Pn|param 1|param 2|param 3|...}}, where "n" is a number, each return the corresponding param n.

They are typically used in other templates when there are several values that can be returned, one of which is the named parameter. Whether to use Pn is calculated.

E.g.

{{ {{#if: {{{1|}}} | P1 | P2 }} |{{{1}}}|{{{2|}}}}}

returns parameter 1 if it's non blank, otherwise parameter 2.

This usage might be chosen because the following more straight forward implementation would have the undesired side effect of stripping whitespace from the beginning and end of parameters 1 and 2 (a side effect of #if:).

{{#if: {{{1|}}} | {{{1}}} | {{{2|}}} }}