The perfect infinitive is used to denote action completed at the time of the main verb: [I am sorry to have wounded you].
+63. Mode.+—A statement may be regarded as the expression of a fact, of a doubt or supposition, or of a command. The power of the verb to show how an action should be regarded is called mode (mood). In our language there is but a slight change of form for this purpose. The distinction of mode which we must make is a distinction that has regard to the thought or attitude of mind of the speaker rather than to the form of the verb.
The indicative mode is used to state a fact or to ask questions of fact:
[I shall write a letter. Shall I write a letter?].
The subjunctive mode indicates uncertainty, unreality, and some forms of condition: [If she were here, I should be glad].
The imperative mode expresses a command or entreaty: [Come here].
+64. The Subjunctive Mode.+—The subjunctive is disappearing from colloquial speech, and the indicative form is used almost entirely.
The verb to be has the following indicative and subjunctive forms in the present and preterite:—
IND. SUBJ. IND. SUBJ.
{ I am I be { I was I were
{ Thou art Thou be { Thou wast Thou were
PRESENT { He is He be PRETERITE { He was He were
{ We are We be { We were We were
{ You are You be { You were You were
{ They are They be { They were They were
In other verbs the indicative and subjunctive forms are the same, except that the second and third persons singular subjunctive have no personal endings.
INDICATIVE Thou learnest He learns
SUBJUNCTIVE Thou learn He learn